In only a week, the already difficult political situation facing Democrats ahead of this fall's midterm elections grew even more troubling. And the bloodletting may not be over.

The latest blows: Vice President Joe Biden's son opted out of a Senate run in Delaware, giving Republicans better-than-even odds of taking over the seat Biden held 36 years, and a moderate Democrat in an Arkansas swing-voting district announced his retirement, the second in as many weeks.

All that comes atop Democrats' loss of Edward M. Kennedy's Senate seat to Republican Scott Brown in Massachusetts, and as the White House builds up its political team to prevent defeats up and down ballots nationwide come November.

"We had a little bit of a buzz saw this week," Obama said at the end of the most politically problematic week of his presidency. That comment was about his endangered health care overhaul plan, but it could extend to electoral politics ahead of his first midterm elections as president.

Just a year ago, Democrats were boasting about the launch of a new era. Obama's party was salivating at the thought of padding its comfortable majorities after several Republicans announced they would retire rather than run again.

Now, Democrats are on defense over big-government, big-spending policies. An anti-Washington wave is sweeping the country. And people are furious over a 10 percent unemployment rate and Wall Street bailouts.

Failed recruitments and growing retirements make it more likely that Democrats will emerge from the 2010 midterms with fewer numbers in Congress, which would pose challenges for Obama's agenda. However, Democrats still are likely to retain control of the Senate, and probably the House, too.

To stanch the bleeding, Obama has turned to his 2008 campaign manager to oversee the White House's midterm efforts from the Democratic National Committee.

"This past week has definitely been a hard one, for all of us," David Plouffe wrote Monday in an e-mail meant to rally Obama backers. "It's at moments like these when we need you most."

Republicans have their problems, too. Cash is one. Others include primary challenges from conservative "tea party" candidates against establishment candidates. And voters still don't have a high opinion of the GOP.

But Republicans have momentum in the wake of Brown's Massachusetts victory. The GOP reports a recruitment windfall in the House and Senate, with on-the-fence candidates emboldened by the more friendly environment.

Video: The next 24: Beau says no
With Brown's win, Democrats control the Senate 59-41. Republicans would need to pick up 10 seats, and not lose any, to gain control. It's not impossible. In January alone, they've found two other ripe opportunities to win Democratic-held seats in the Senate

Beau Biden's decision to pass up a Senate run to run for re-election as Delaware's attorney general automatically made Republican Rep. Mike Castle, a popular former governor, favored to win. In bowing out, Biden cited not the thorny political environment but a need to focus on prosecution of high-profile child molestation case.

Also at risk is Democratic Sen. Byron Dorgan's seat in conservative-tilting North Dakota. Stunning Democrats, Dorgan said just after the new year that he would not seek re-election. North Dakota's Republican governor, John Hoeven, quickly jumped into the race. Democrats haven't fielded a candidate yet.

Democrats' woes in the Senate are partly of Obama's own making. He plucked several Democrats from the Senate to fill his administration, and those seats also are now vulnerable.

Sen. Michael Bennet of Colorado, appointed to fill Interior Secretary Ken Salazar's term, is in a primary, and Sen. Kirsten Gillibrand, appointed to fill Secretary of State Hillary Rodham Clinton's seat, also may face a primary challenge. The GOP is competing hard for Obama's old seat; Sen. Roland Burris, who was appointed to the seat, is not running.

Following Connecticut Sen. Chris Dodd's retirement, Washington insiders have been on high alert for hints that other troubled Senate Democrats will bow out to make way for stronger candidates.

Among the most vulnerable incumbents: Senate Majority Leader Harry Reid of Nevada and Blanche Lincoln of Arkansas. Given a political environment tipping its way, the GOP also is keeping an eye on Sens. Barbara Boxer in California and Arlen Specter in Pennsylvania.

In the House, Republicans need a net gain of 40 seats to take back control. That's a long shot, but less of one than it was at the start of 2010.

Two moderate Democrats in as many weeks in Arkansas' swing districts have chosen to retire rather than face re-election in a problematic political environment. The retirements of Reps. Vic Snyder and Marion Berry bring to 12 the number of Democratic House retirements, compared with 14 for Republicans.

Democrats, however, fear privately that they are just the first ripples in what could become a flood of House retirements creating pickup opportunities for Republicans.

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